High strength ceramic-like article containing alpha quartz as the major crystal phase



United States Patent HIGH STRENGTH CERAMIC-LIKE ARTICLE CON- TAINING ALPHA QUARTZ AS THE MAJOR CRYSTAL PHASE Francis J. Shonebarger, Lancaster, Ohio, assignor to Allehor Hocking Corporation, Lancaster, Ohio, a corporation of Delaware No Drawing. Filed Nov. 12, 1965, Ser. No. 507,567

Int. Cl. C04b 33/16 US. Cl. 106-39 11 Claims ABSTRACT OF THE DISCLOSURE A ceramic article produced by the controlled divitrification of a glass consisting essentially of about 55.0 to 66.0% by weight SiO 9.0 to 23% by weight A1 0 8.5 to 13.7% by weight MgO, 1.0 to 7.0% by weight B 0 1.0 to 6.0% by weight TiO and 2.0 to 2.75% by weight ZrO The article produced contains alpha quartz as the major crystalline phase.

This invention relates to the production of ceramiclike articles by the controlled devitrification of vitreous articles and more particularly it relates to a method for producing high-strength, ceramic-like articles having desirable coefiicients of thermal expansion.

Controlled devitrification of vitreous articles has been practiced since Reaumur devitrified wine bottles in the early 1700s. In recent years more modern technology has made it possible to commercially produce ceramic-like articles, which can withstand severe temperature changes, from vitreous articles.

More recently, remarkably high strength ceramiclike products have been produced from vitreous articles. Such high strength articles are shown in Henry et al. US. Patent No. 3,117,881. These' articles are produced from vitreous base compositions which upon being completely or almost completely devitrified will yield a predominant crystalline phase of cordierite, mullite, sapphirine or tridymite. In this process at least 6% of a primary nucleating agent ZrO and about 1.5% of a secondary nucleating agent are employed.

Ceramic-like articles having a minor crystalline phase of quartz are shown in Stookey U.S. Patent No. 2,971,853. Such articles are produced from a base composition comprised of Li O, A1 0 and SiO by using a photosensitive nucleating agent.

Heretofore, it has not been possible to produce ceramiclike articles having a major crystalline phase of quartz through the use of non-photosensitive nucleating agents from a glass consisting predominantly of MgO, A1 0 and SiO The present invention provides a high strength ceramiclike article having a major crystalline phase of alphaquartz, of varying degrees of purity, produced from a glass consisting predominantly of MgO, Al O and SiO It has been found that the coefiicient of thermal expansion of the present ceramic-like article can be controlled within broad ranges by varying the heat treatment rendering themespecially suitable for tableware. This property permits one to control the strain in the article and in an applied glaze.

One important advantage of being able to control the coefficient of thermal expansion is that conventional glazes can be applied to the tableware articles made from my ceramic-like article. This has not heretofore been possible with many of the previous ceramic-like articles produced by devitrifying glasses because the coefficients of thermal expansion of the ceramic-like articles have not coincided with those of the available glazes and,

'ice

consequently, when the glazed ware was tired and cooled, cracking occurred, or, when the glaze was fired the article deformed.

Unlike prior methods utilized to produce ceramic-like articles from virteous compositions, such as those referred to above, the present method does not seek to produce a product which is completely or almost completely crystalline. Through X-ray diffraction analyses, which can at best provide only a rough approximation of the crystal content of a devitrified article, I have found that articles produced in accordance with the present invention contain less than about 40% by volume of alphaquartz. Alpha-quartz is the major crystalline phase present, that is, it is always present in an amount greater than any other crystalline phase and usually in an amount substantially greater than any other crystalline phase.

My invention consists of heat treating a vitreous composition which includes, on an oxide basis, about 55.0 to 66.0% by weight SiO 9.0 to 23.0% by weight A1 0 8.5 to 13.0% by weight MgO, 1.0 to 7.0% by weight B 0 1.0 to 6.0% by Weight TiO and 2.0 to 5.75% by weight ZrO to provide a ceramic-like material which contains alpha-quartz as the major crystalline phase.

The ceramic-like materials so formed, which contain alpha-quartz as a major crystalline phase, have a modulus of rupture ranging from about 30,000 p.s.i. to about 180,000 p.s.i. The coefiicients of thermal expansion ranges between about 34 10 C. and X10-/ C. The modulus of rupture and the coefficient of thermal expansion can be varied by the heat treatment and the composition.

I have found that surprisingly a ceramic-like article containing alpha-quartz as a major crystalline phase can be produced from a vitreous article consisting essentially of MgO, A1 0 and SiO only when B 0 ZrO and TiO are present in amounts to be more fully set forth below.

Although the exact mechanism by which alpha-quartz is produced as a major crystalline phase and the reason why B 0 ZrO and TiO are all essential is unknown, it believed that the phenomenon of short-range-order phase separation is involved. It is believed that when B 0 is used with the present compositions, a metastable condition is produced in the glass and that only thereafter can alpha-quartz be crystallized through the combined use of TiO and ZrO The presence of TiO and ZrO is necessary to crystallize an alpha-quartz crystalline phase which is responsible for the unique properties of my ceramic-like article. If either the TiO or the ZrO is omitted, alpha-quartz can not be crystallized upon heat treatment.

Not only is the effect of the metastable condition necessary for the subsequent crystallization of the alphaquartz, but it also prevents deformation of the glass article during the controlled heat treatment of the ware to mature a glaze or a decoration. Additionally, the result of the metastable condition contributes to the opaqueness of the articles.

The glass batches from which the present ceramic articles may be produced can be compounded from ordinary glass making ingredients. Conventional glass melting and forming techniques and apparatus can likewise be employed in the fabrication of articles from the glass.

Table I shows five compositions which can be heat treated to produce a ceramic-like article having an alphaquartz crystalline phase.

From the batch material shown in Example 1, a glass batch was compounded and melted to give a glass hav ing an oxide analysis identical to that shown as Example 1. The batch melted readily at 2700 F. After melting, a rod was drawn from the glass. The rod was cooled to room temperature andreheated to 1800" F. at the rate of 100 F. per hour and held for one-half hour. It was then TABLE 111 Maximum cryscooled to roon} te mperature' tallizing tempera- Coetf. thenn.

The ceramic-like rod so produced was white and hure 100;11 :111 exp. opaque. Examination by X-ray d1firact1on, usmg the tech- 3 3 ea up Time held (ht) strength, PM. n1ques set forth in Klug and Alexander X-Ray Dlffraction Procedures, disclosed the presence of alpha-quartz. i538: gggg 313 331383 Thermal expansion tests performed on the rod confirmed 1,800.- 4 67.3 53,800 the presence of alpha-quartz by the characteristic inveri288: 53:? 588 sion of quartz.

strength of f Whlch was about lnches m It can be seen from Table II that as the heating rate is d1an1 eter determmed by a conventlonal three increased, the coefiicient of thermal expansion and the loadmg techmque and was found to be about strength decrease. Likewise, it can be seen from Table Glass rods were Produced from the glass composltlons III that as the holding time at the maximum crystallizing of. Examples 2-5. The rods from Examples 2, 3, a 4 temperature is increased, the coeflicient of thermal exwere heat treated at 1800 F. for one-half hour, and the Pansion incrases rod from Example 5 was heat treated at 1700 F. for tWO TiO ZrO and B 0 must be present in certain amounts hours. X-ray d1ftract1on analyses showed the presence of in order to obtain h-rystals of alpha quartz alpha-quartz. The strengths analyses showed the presence )0 Table IV contains five examples of glasses having a of alpha-quartz. The strengths of the rods ranged from o A1203 and o content Within the ranges of the 34,800 to 125,109 present invention but which include only TiO TiO with The deformatlon of the rods during the crystallization B203, or Tioz with ZrO2 heat treatment was measured by observing the angular T BLE v deviation from the horizontal which had occurred in an A I unsupported three-quarters of an inch of the rod. As can Oxide 6 x- 7 Ex. 8 Ex 9 Ex. 10 be seen from Table I, the rods did not deform during the m 78 heat treatment. B203--- FezOs- 0.07 4-22 TABLE I h5g 13 25 Batch Material Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 O 82 a .05 ggggg ggf ffi Heat Treatment, F 04,700 0-1, 700 0-1, 800 0-1, 800 01, 800 426.5 450 378 1 387 1 207 0 0 ,1 3507 4725 Rods made from Examples 8-10 were sub ected to 127.0 134 134 17M 18M 18 184-5 18 X ray d1tfract1on analyses after they were heat treated. 110, They d1d not produce an X-ray trace correspondmg to alpha-quartz. None of the rods from these examples possessed the combined properties of strength, coefiicient of 40 thermal expansion, low deformation characteristic,

Oxide content Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5

63. 53 03. 58. 7s 61. 41 58. 4. 86 1.88 1.83 1.85 1.89 0.07 0.08 0.04 0.04 0. 04 3.88 3. 89 3.78 3.83 3. 91 10.85 13.86 18.36 20. 50 22. 94 0.16 0.16 0.13 0.11 0.11 12.97 13. 00 1o. 53 8. 69 8.88 3.63 3.64 8.54 a. 58 s. 66 0.04 0.06 i i' 2600 "i0""""2i00 46,500 34, 800 40, 600 125,100 80,000 73.3x10- 0 0 0 0 opaqueness and the white color of the ceramics produced according to my invention. It has been found that the heat treatment given to the It 1.121s also been found that to produce a ceramlc havmg at 11121101 crystal phase of alpha-quartz that not only must formed article affects the physical properties of the finished article. The heating rate during the crystallizing cycle should be within the range of about 33 F. per hour to 300 F. per hour when the rods are being reheated above 1300" F. The maximum crystallizing temperature should be below 1900 F. The article may be held up to two hours at the maximum crystallizing temperature.

Tables II and III show the results of subjecting rods made from the compositions of Example I to various heating rates and holding periods.

TABLE V Ex. 11 Ex. 12 Ex. 13 Ex. 14

TABLE II Coefficient thermal Heating rate, F. per expansion 1 0. hour to 1,800 F., 1 hour (X10 HID-600 F. Strength, p.s.i.-

crystalline phase. Even though the B 0 level can be raised to slightly above 6% when the ZrO and T iO contents are raised, it has been found that more than 7% greatly inhibits or altogether prevents the formation of alpha-quartz crystals.

Table VI shows three glasses having varying amounts of ZrO but otherwise they are substantially identical. Example 1 could also be included in this table.

TABLE VI Ex. Ex. 16 Ex. 17

Rods drawn from these glasses and heat treated by heating to 1800 F. and holding for /2 hour showed a decrease in strength from 45,800 p.s.i. for the rod made from the glass of Example 1 to 26,600 p.s.i. for the rod made from Example 16. The rod made from the glass of Example 17 was not suitable for testing. If the TiO content is increased as the ZrO content is being increased, the decrease in strength is not as marked. However, more than about 5.75% ZrO will generally precipitate when the glass is being melted.

Table VII shows six glass compositions which were melted, formed into rods and crystallized at 1800 F. for /2 hour to study the effect of varying the TiO content and the TiO and Zr0 content.

TABLE VII Oxide Ex. 18 Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23

SiO2 63. 94 63. 32 62.30 59. 99 63. 48 62.44 B:Oa 3. 26 3. 23 3. 18 3. 06 3. 22 3. 14 Fe20 07 07 07 07 07 .07 T102.-... 4. 89 5. 81 7. 34 10. 76 4. 82 5. 65 A1203... 10. 92 10. 81 10. 64 10. 10.76 10. 50 C30..- 16 16 16 15 16 .15 MgO... 13. 06 12. 93 12. 72 12. 25 12. 86 12.55 Nfl20 0. 04 0. 04 0. 04 0. 04 0. 04 0. 04 Z10: 3. 66 3. 62 3. 56 3. 43 4. 59 5. 46

Rods made from the glasses of Examples 18, 19, 22 and 23 showed the presence of alpha-quartz upon X-ray diffraction examination while the rods made from the glasses of Examples 20 and 21 did not.

It was found that the TiO content could slightly exceed 6% if the ZrO- content was also raised. However, no advantages were obtained by raising the TiO content above 6%.

The glasses shown in Table VIII can also be crystallized to produce a useful ceramic-like article containing a major crystalline phase of alpha-quartz.

TABLE VIII Oxide Ex. 24 Ex. 25 Ex. 26 Ex. W Ex. 28 Ex. 29

SiOz. 61. 85 60. 61 59. 79 59. 62. 49 62. 53 A120 21. 33 20. 90 21. 36 22. 46 14. 88 16. 91 MgO 9.04 8. 86 9.06 8. 69 13. 01 10.97 BZO 1. 92 1. 88 1. 93 1.85 1. 88 1. 88 Z103.-. 3. 73 3. 65 3. 73 3. 58 3. 64 3. 65 TiO2 1. 98 3. 95 3. 99 3. 83 3. 89 3. 9O CaO .11 11 11 11 16 13 F8203 .04 .04 .04 .03 .05 .04

When rods made from the glasses 24, 25 and 27 were heated to 1700 F. for two hours, alpha quartz was found to be the major crystalline phase formed. The rods were tested and found to have strengths ranging from 34,700 p.s.i. for the rod made from the glass of Example 24 to 148,300 p.s.i. for the rod made from the glass of Example 25.

Rods made from the glasses of Examples 26, 28 and 29 were heated to 1800 F. for /2 hour. A major crystalline phase of alpha quartz was found. The stengths of the rods measured in p.s.i. were respectively 185,700, 62,900 and 43,400.

TABLE IX Ex. 30 Ex. 31 Ex. 32 Ex. 33

60. 00 56. 68 59. 40 58. 23 18. 74 19. 55 20. 49 20. 08 10. 75 8. 29 8. 69 8. 51 1. 86 5. 29 1. 1.81 3. 61 3. 41 3. 58 3. 51 3. 86 3. 65 3. 82 3. 75 13 10 11 10 O4 03 03 03 1. 00 3. 00 ZnO 2. 04 3. 97

Ex. 34 Ex. 35 Ex. 36 Ex. 37

36. 80 64. 07 64. 56 64. 69 4. 06 4. O8 3. 29 3. 30 0. 07 11 14 04 3.90 3. 91 3. 94 3. 10.88 10. 93 11. 02 11. 03 0.11 0. 11 0.12 0.10 13.02 12. 09 11.66 12.70 0. 05 O. 06 0. 06 0. 04 3. 58 3. 60 3. 63 3. 63 0. 02 0. 04 0. 06 0. 50 1. 00 1. 51 LiF 0. 50

Ex. 38 Ex. 39 Ex. 40 Ex. 41

Rods made from the glasses of Examples 30 and 34-41 were heated to 1800 F. and held for /2 hour and rods made from the glasses of Examples 31, 32 and 33 were heated to a peak temperature of 1700 F. A major crystalline phase consisting of alpha-quartz was detected in each rod. The strengths of the rods varied from a low of 40,700 p.s.i. to a high of 153,300 p.s.i.

It has been stated earlier that conventional glass making apparatus and batch materials may be utilized in the practice of this invention. Due to the volatility of B 0 the B 0 content of the synthesized article is dependent upon the melting technique and the content may vary even though the amount added to the batches is identical. For instance, the glasses of Examples 1 and 12 were melted by a technique different from the other examples. It was found that the ceramic-like articles produced from these two glasses had an analyzed B 0 content of about 1% less than the calculated amount while the others had an analyzed content approximately equal to their calculated content. It should therefore be understood that the B 0 ranges specified herein refer to analyzed percentages.

Having thus described my invention, I claim:

1. A ceramic-like article produced by the controlled thermal devitrification of a glass consisting essentially of 55.0 to 66.0% by weight SiO 9.0 to 23.0% by weight A1 0 8.5 to 13.7% by weight MgO, 1.0 to 7.0% by weight B 0 1.0 to 6.0% by weight TiO and 2.0 to 5.75% by weight Z1 0 said article containing alpha-quartz as the major crystalline phase.

2. The ceramic-like article of claim 1 wherein said glass includes 1 to 5.0% by weight of at least one flux selected from the group consisting of ZnO and PhD.

3. The ceramic-like article of claim 1 wherein said glass includes .5 to 2.0% by weight of at least one flux selected from the group consisting of Li O, LiF and CaF 4. The ceramic-like article of claim 1' wherein the combined weight of SiO A1 and MgO is at least 85.0%.

5. The ceramic-like article of claim 4 wherein said glass also includes 1.0 to 4.5% by weight of at least one flux selectedirom the group consisting of ZnO, PbO, Li O, LiF and Cal-"' 6. A ceramic-like article produced by the controlled thermal devitrification of a glass consisting essentially of 58.0 to 61.0% by weight SiO 15.0 to 20.0% by weight A1 0 8.5 to 11.0% -by weight MgO, 1.75 to 3.0% by weight-B 0 2.5 to 4.0% by weight TiO and 3.5 to 4.0% by weight ZrO said article containing alpha-quartz as the major crystalline phase.

7. A method of making a ceramic-like article, having a coefiicient of thermal expansion of from 34X C. to 125x10 C. and a modulus of rupture from 30,000 psi. to 180,000 p.s.i., comprising the steps of melting a vitreous composition consisting essentially of 55.0 to 66.0% by weight SiO 9.0 to 23.0% by weight A1 0 8.5 to 13.7% by Weight MgO, 1.0 to 7.0% by weight B 0 1.0 to 7.0% by weight TiO and 2.0 to 5.75% by weight ZrO forming an article from said vitreous com position, heating the article to a temperature of between 1700-1900" F. at a rate of 33 to 300 F. per hour and holding said article at said temperature for a period from minutes to two hours to produce alpha quartz as the major crystalline phase.

8. The method of claim 7 wherein said glass includes 1 to 5.0% by weight of at least one flux selected from the group consisting of ZnO, PbO, Li O, LiF and CaF 9. The method of claim 7 wherein the combined weight of SiO A1 0 and MgO is at least 85.0% by weight.

10. In a method of making a high-strength ceramiclike article having a modulus of rupture of over 100,000 p.s.i., the steps of melting glass batch materials and forming a glass article consisting essentially of 60.61% SiO 20.90% A1 0 8.86% MgO, 1.88% B 0 3.65% ZrO and 3.95% TiO heating said'article at a rate of about 100 F. per hour-to a temperature of about 1700 F, and holding said article at about 1700 F. for about 2 hours.

11. In a method of making a high-strength ceramiclike article having a coeflicient of thermal expansion of about 73.3 10' and a modulus of rupture of about 46,500 p.s.i., the steps of melting glass batch materials and forming a glass article consisting essentially of 63.53% SiO 4.86% B 0 3.88% TiO 10.85% A1 0 12.97% MgO, and 3.63% ZrO heating said glass article at a rate of about 100 F. per hour to a temperature of about 1800 F., and holding said article at 1800 F. for about /2 hour.

References Cited UNITED STATES PATENTS 3,116,137 12/1963 Yasilos et a1 10652 X 3,117,881 1/1964 Henry et a1 l0639 3,205,079 9/1965 Stookey 106-39 3,252,811 5/1966 Beall 10639 3,380,818 4/1968 Smith 106-39 X HELEN M. MCCARTHY, Primary Examiner W. R. SATTERFIELD, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,485,644 Dated December 23. 1969 Inventor(s) Francis Joseph Shonebarggr It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, Line 28, "125 x l0'/C." should be --125 x 10' /c.-- I

Column 3, Lines 19 and 20, delete "The strengths analyses showed the presence of alpha-quartz."

Column 3, Table I, Example 1, "73.3 x 10' should be --73.3 x 10' /c.--

Column 3, Table II, "3 l/3" should be --33 l/3-- Column 6, Line 2, "can below" should be -can be below-- Column 6, Table IX, "36.80" should be --63.80--

SIGNED Mm SEALED JUN9 1970 3 ,Atteat:

WILLIAM E. scram. m. Edward M. Fletcher. In Commissioner of Putin Atteating 0mm FORM PO-1D5OH0-69) USCQMM OC 603764369 0 u s oovznnuzm rammuc ornce lass n-na-ssn 

